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Well, Chris, since your prop is also a Catto and sounds
suspiciously like Sam's with that chord dimension, it will be interesting to see
if you get much beyond 5500-5600 even airborne.
At 5000 rpm a N/A rotary can produce in the vicinity
of 125-140 HP, that is sufficient to keep an Rv airborne with no problem.
Take off and climb out is where you will notice the absence of HP. So as
long as you have a decently long runway, I don't see any problem, but I think I
would want one close to 3000 hard surface especially in warmer weather. I
flew my first 160 hours with around 130 HP - but 180HP is much, much
nicer.
Ed
Sent: Tuesday, October 05, 2010 9:09 PM
Subject: [FlyRotary] Re: Sam Hodges Prop area
Comparison
Ed,
I
checked today, and mine has an 8.25 (quickly measured, not accurately)
cord. Time will tell about what RPM I get and if I will have to trim the
prop. I’m reminded of the line from the movie “Guys and Dolls”. I
don’t think I want to take the bet and end up with an ear full of
cider.
I
got the new radiator today, so bracket construction and installation can
begin.
Chris
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed
Anderson
Sent: Monday, October 04, 2010 7:20 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Sam Hodges Prop area
Comparison
Based on my
own experience and many others, its not usually to have the starting HP be a bit
lower than what you end up with after sorting things out. Always best to
wait a bit before trimming the prop - I know folks who have trimmed theirs and
later wish they had not.
But, if you
have anywhere close to 8" of cord, then I'll bet a beer or two you'll be sending
it back - even with a turbo that prop would have been hard to push past 6000 rpm
static.
Sent: Monday, October 04,
2010 5:58 PM
Subject: [FlyRotary] Re: Sam
Hodges Prop area Comparison
Ed,
I
will measure next time I am at the airport. But I know I will be closer to
Sam’s numbers. My prop looks exactly like his.
This
makes me feel a little better, as I was wondering why my static was so low
compared to other’s numbers.
I
still think I will get airborne again, and actually check out what my dynamic
max RPM is before I make any changes.
Chris
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed
Anderson
Sent: Monday, October 04, 2010 6:58 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Sam Hodges Prop area
Comparison
With Sam's
original prop, he got around 5000 rpm max static. May have been as high as
5100 but ranged around 4800-5000 rpm. When He put my 74x88 Performance
Prop on he got as high as 6100 rpm one time but each time got at least 6000
rpm.
Measure your
chord at its widest point - mine is 5 1/2", Sam's was around 8" - not the whole
story on a prop, but can be an indication of whether your prop is close to one
end of the spectrum or the other
Sent: Sunday, October 03,
2010 9:37 PM
Subject: [FlyRotary] Re: Sam
Hodges Prop area Comparison
Ed,
I
have the same Catto prop and mine is marked 76x88. I didn’t get more than
5000 RPM max static either. To be honest, I didn’t look at the max RPM
while airborne, I was too busy looking at the temp, and I pulled the power back
as soon as I could. I hope to fly again with the new radiator in a few
weeks, and should be able to get new data. What were Sam’s numbers Max
static with the CATTO and with your prop?
Thanks,
Chris
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed
Anderson
Sent: Sunday, October 03, 2010 10:46 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Sam Hodges Prop area
Comparison
Just doing a
rough back of the envelope calculation comparing Sam Hodges prop (8" cord)
to my prop (5 1/2" cord) and assuming the two props blade profiles were similar,
Sam's prop would have approx 45% more prop area trying to push the air back than
my prop. Small wonder his engine was groaning trying to spin it up to 6000
rpm.
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